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WHAT IS GIS?

Geographic Information Systems (GIS)

GIS is a system of hardware and software used for storage, retrieval, mapping, and analysis of geographic data. Practitioners also regard the "total GIS" as including the operating personnel and the data that go into the system, as well as the policies, procedures, training and any other item or issue that effect the system.

Spatial features are stored in a coordinate system (latitude/longitude, state plane, UTM, etc.), which references a particular place on the earth. Descriptive attributes in tabular form are associated with spatial features. Spatial data and associated attributes, in the same coordinate system, can then be layered together for mapping and analysis. GIS can be used for scientific investigations, resource management, and development planning.

GIS differs from CAD and other graphical computer applications in that all spatial data is geographically referenced to a map projection in an earth coordinate system. For the most part, spatial data can be "re-projected" from one coordinate system into another, thus data from various sources can be brought together into a common database and integrated using GIS software. Boundaries of spatial features should "register", or align properly, when re-projected into the same coordinate system. Another property of a GIS database is that it has "topology," which defines the spatial relationships between features. The fundamental components of spatial data in a GIS are points, lines, polygons and raster data. When topological relationships exist, you can perform analyses, such as modeling the flow through connecting lines in a network, combining adjacent polygons that have similar characteristics, and overlaying geographic features."

In general, GIS has an "identity issue" and has yet to settle on an all-inclusive definition. Is it is a "process", a software, or is it defined by its properties, purposes, needs and its users? Furthermore, there is no absolute answer as to the relationships of GIS to Information Technology (IT), Remote Sensing, Cartography, Surveying, Photogrammetry, Mapping, etc. The truth is that "GIS" is all of these and more... All of the "parts" combine in a synergistic way, that is still evolving. With this in mind, The Ohio Department of Transportation and the Office of Environmental Services is constantly striving to find creative, new, better ways to take advantage of this power. The goal is to allow decisions to be arrived at in an accurate, cost effective and simple process.

ODOT uses GEOMEDIA, by Intergraph Corporation,  as the department-wide, GIS standard.  

The major uses for GIS in the Office of Environmental Services, are for RED FLAG MAPPING and for GIS LITERATURE SEARCHES, although  GIS has an infinite number of possible applications.

September 04, 2008

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